Hepatitis C Lingo: What is a Log?

Okay, you are going into treatment.  You must understand the language of treatment progress. No one values your health more than you.

Getting information off the Internet is like taking a drink from a fire hydrant.   Mitchell Kapor

 Treatment response is a topic of great importance to me, you, and doctors.  They need  to see if the treatment is working enough to keep poisoning you.

Viral load is how to measure response. It’s done  by looking at the amount of virus in your blood. Viral load is checked before treatment,  at week 4, 12, and either 24 or 48, depending on duration of therapy, then 24 weeks (6 months) after therapy.   The response is measured in log reduction.    In fact log stands for logarithmic.  So what?  Each log corresponds to a factor of 10.  So what?  A 1-log reduction means virus decreases by 10 times; a 2-log = 100, a 3-log = 1,000, a    6-log reduction = 1,000,000 = 1 million.  Log is a way of not writing down all the zeros.  Just count the zeros gone and you get the number of viruses that died per ml of blood and went away.  Sort of.  There, in one paragraph we discussed a concept that took me some time to learn.  And you thought you would never use that math junk.

When I was in middle and high school, I had it in my head that my brain wasn’t “smart enough” for math and chemistry, even though I skipped kindergarten and the 2nd half of my senior year.   So I avoided the hard sciences.  Remember I was still GOD, grown up on duty, at my house. Then in my 20s, I went to college and I decided I didn’t want to fear math and chemistry any more. I took inorganic chemistry with algebra on the side to understand the language of thermodynamics.  This is an example of how my childhood perceptions always played down my abilities even though my family said I was smart (which I loved but didn’t believe) . I graduated from pharmacy school at 30,  then went back for a Dr. of Pharmacy in my 50s (while traveling around the country for work and, unaware that Hep C was dragging me down).

Why am I interjecting these little stories in the middle of scientific drama?  Because there is no scientific drama!

All measures must have units:  pounds of pressure per square inch (PSI), miles per gallon (MPG), ears of corn per stalk (one).  Notice the word per in each. The  Hepatitis C virus (HCV) is number of copies of the virus per ml of blood. The hepatitis C virus, like all viruses, cannot reproduce by itself. It must first infect a living cell, such as the hepatocyte, and take over the cell’s “machinery.” Using the genetic information in your cell, the hepatitis C virus is able to make copies of itself which can go on to make more copies.  The virus is measured in copies per ml of blood.  I know, weird.

Lindenbach B, Rice C (2005). “Unravelling hepatitis C virus replication from genome to function”. Nature 436

BTW, kids in Middle School know this stuff.  Amazing.    We will talk about RNA another time.  I know you can hardly wait.

Source:  Vertex website, Wikipedia

http://www.vrtx.com/assets/pdfs/VRTXHCVTreatmentResponse.pdf

www.wikipedia.com

and my brain: no link

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